Survival and multiplication of Gaeumannomyces graminis var. tritici (the wheat take-all fungus) and related fungi on different wild and cultivated grasses

The susceptibilities of different grass species, including currently important annual weeds of cereal crops, to root infection by Gaeumannomyces cylindrosporus and related weakly or non-pathogenic fungi, and to G. graminis var. tritici (the take-all fungus), were tested in pot experiments. Amounts of infection on wheat grown subsequently were also compared. Infection by the non-take-all Gaeumannomyces spp., arising from artificial inoculation, was variable but characteristic swollen cells were often more numerous in root systems of wheat than of grasses. Take-all, arising from natural soil infestation, in the following wheat was decreased only after inoculation of the grasses with G. graminis var. graminis in one experiment; this effect was not influenced by previous host species. Wheat became more affected than grasses by take-all but bromes (Anisantha sterilis and Bromus secalinus) were more diseased than the other grasses. Overall, annual grasses, including the bromes and black-grass (Alopecurus myosuroides), developed more take-all than perennial grasses. The most affected species allowed most take-all to develop on wheat plants grown subsequently. Where a second sowing of wheat was tested (i.e. a total of three sowings), take-all after the perennial grasses was similar to or more than that after annual grasses or wheat. Implications for the effects of weed grasses on take-all in modern cereal cropping systems, particularly those involving set-aside, are discussed.